OTRC: Katie Couric to guest-host 'GMA,' poses with DJ Pauly D (Photo)

Katie Couric Tweeted this photo of herself with DJ Pauly D on March 29, 2012. / Katie Couric and anchor George Stephanopoulos appear in a photo provided on March 29, 2012, by the ABC Network, whose parent company, Disney, owns OnTheRedCarpet.com. Starting on April 2, Katie Couric will return to morning television by guest-hosting the ABC show 'Good Morning America' for one week while Robin Roberts is on vacation. (twitter.com/katiecouric/status/185369227765612549 / Fred Lee)

Katie Couric is set to co-host "Good Morning America" next week, almost six years after she left NBC's "Today" show - the ABC program's longtime competitor.

Starting on Monday, April 2, the 55-year-old veteran newswoman will take over for Robin Roberts while she is on vacation and host the show with George Stephanopoulos (pictured, above), ABC announced on Thursday.

Couric left her job as co-host of the "Today" show in 2006 after 15 years and joined the CBS "Evening News," becoming the first woman to anchor a network evening newscast on her own. The journalist, who has interviewed U.S. presidents and movie stars, exited the series in 2011 and joined ABC. She will host a new syndicated daytime talk show, "Katie," on the network this fall.

Couric began her television career as a news assistant at ABC News in Washington, D.C. in 1979. She did grunt work - making photocopies and coffee and fetching ham sandwiches. Couric later went on to work for CNN and for NBC and began co-hosting "Today" in 1991. The news woman, known for her on-air sunny demeanor, was dubbed "America's Sweetheart" by critics during her run.

The series has beaten "Good Morning America," also called "GMA," in weekly average ratings since December 1995. The race is heating up. Nielsen Media research shows that last week, "GMA" had 4.84 million viewers, while "Today" had 4.98 million, marking a margin of 137,000 - the closest between the two since 2008.

"GMA" also earned higher ratings than "Today" for its March 19 episode, which had 48,000 more viewers, and on March 23, which had 13,000 more. Since the start of 2012, weekday episodes of "GMA" have been watched by an average of 4.93 million people versus the "Today" show's 5.38 million.

Couric has also appeared on "GMA" before but not as a co-host. She first appeared on the show in May 2008, when she worked for CBS, along with ABC's Charles Gibson and NBC's Brian Williams in a bid to promote the "Stand Up to Cancer!" special. Couric's husband Jay Monahan died of colon cancer at age 42 on 1998.

Couric talked about colon cancer prevention on "GMA" on March 14 and appeared on the show three times in 2011. Also that year, she was a guest co-host on the ABC daytime show "LIVE! With Kelly."

Her new ABC talk show premieres on September 10. "I think if you put on a quality show and you discuss things that people want to talk about and you make it compelling and accessible and relatable, I think, I hope, if you build it, they will come, like they say in 'Fields of Dreams,'" Couric told OnTheRedCarpet.com in June 2011. "I think, hopefully, there will be an appetite for smart conversation, for fun discussions, for all sorts of different things and that what I hope to bring to the table."